Ｗe believe such improvement in pulmonary mechanics, which may reflect in the weaning parameters that respiratory therapist measured before weaning program, may be different after tracheostomy creation, especially in those patient with weaning failure. Ｗe therefore hypothesized that there may be an improvement in pulmonary mechanic for patients with weaning failure after tracheostomy, and that this improvement may be able to predict the subsequent successful weaning from mechanical ventilator support. Hereby the investigators perform a prospective single-center study to investigate the changes of weaning parameters in weaning failure patients after tracheostomy as a predictor of successful weaning.